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Chapter Analysis
Advanced30 pages • EnglishQuick Summary
This chapter explores the structure and function of DNA, detailing its double-helix formation and role as the genetic material. It discusses processes such as DNA replication, transcription, and translation, emphasizing the central dogma of molecular biology. The chapter also covers the discovery and significance of the genetic code, and the regulation of gene expression. Finally, it examines the Human Genome Project and DNA fingerprinting as applications of understanding the molecular basis of inheritance.
Key Topics
- •Structure of DNA and double helix model
- •DNA replication
- •Transcription and types of RNA
- •Genetic code and protein synthesis
- •Regulation of gene expression
- •Human Genome Project
- •DNA fingerprinting
- •RNA world and origin of life
Learning Objectives
- ✓Understand the molecular structure and function of DNA
- ✓Describe the processes of transcription and translation
- ✓Explain the role and significance of the genetic code
- ✓Illustrate how gene expression is regulated in cells
- ✓Discuss the applications of DNA technology in genomics
- ✓Explore the experiments that determined DNA as the genetic material
Questions in Chapter
Group the following as nitrogenous bases and nucleosides: Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.
Page 109
If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.
Page 109
If the sequence of one strand of DNA is written as follows: 5' -ATGCATGCATGCATGCATGCATGCATGC-3'. Write down the sequence of complementary strand in 5'→3' direction.
Page 109
If the sequence of the coding strand in a transcription unit is written as follows: 5' -ATGCATGCATGCATGCATGCATGCATGC-3'. Write down the sequence of mRNA.
Page 109
Which property of DNA double helix led Watson and Crick to hypothesise the semi-conservative mode of DNA replication? Explain.
Page 109
Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesised from it (DNA or RNA), list the types of nucleic acid polymerases.
Page 109
How did Hershey and Chase differentiate between DNA and protein in their experiment while proving that DNA is the genetic material?
Page 109
Differentiate between the followings: (a) Repetitive DNA and Satellite DNA, (b) mRNA and tRNA, (c) Template strand and Coding strand.
Page 109
List two essential roles of ribosome during translation.
Page 109
In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after the addition of lactose in the medium?
Page 109
Explain (in one or two lines) the function of the following: (a) Promoter, (b) tRNA, (c) Exons.
Page 109
Why is the Human Genome project called a mega project?
Page 109
What is DNA fingerprinting? Mention its application.
Page 109
Briefly describe the following: (a) Transcription, (b) Polymorphism, (c) Translation.
Page 109
Additional Practice Questions
What is the primary structure of DNA and how does it contribute to its overall stability?
mediumAnswer: The primary structure of DNA consists of a sugar-phosphate backbone and nitrogenous bases. The stability of DNA is largely due to the hydrogen bonds between complementary bases and the hydrophobic interactions among the stacked bases, which help maintain the helical structure.
Explain the process of DNA replication and its significance.
hardAnswer: DNA replication involves unwinding the double helix, followed by synthesizing a new complementary strand for each original strand. This semi-conservative method ensures that each daughter cell receives an exact copy of the DNA during cell division.
Describe the role of tRNA in protein synthesis.
mediumAnswer: tRNA serves as an adaptor molecule translating the triplet codons in mRNA to the correct amino acids. Each tRNA molecule carries a specific amino acid and contains an anticodon that matches the mRNA codon, ensuring the correct sequence of amino acids in the resulting polypeptide.
Why is transcription regulation crucial in gene expression?
mediumAnswer: Regulating transcription is crucial because it determines when and how much of a gene's product will be synthesized. It is a key point of control in cellular function, growth, and differentiation, enabling cells to respond to changes in their environment.
How does RNA splicing differ between eukaryotes and prokaryotes?
easyAnswer: In eukaryotes, RNA splicing involves removing introns and joining exons from the pre-mRNA. In prokaryotes, splicing is not required as prokaryotic genes are typically continuous without introns.
Discuss the impact of mutations on the genetic code and protein synthesis.
hardAnswer: Mutations can lead to changes in the genetic code, which may alter the amino acid sequence of proteins. Such changes can disrupt protein function, potentially leading to genetic disorders or diseases but also serving as a source of genetic variation and evolution.
Illustrate the central dogma of molecular biology.
easyAnswer: The central dogma of molecular biology explains the flow of genetic information within a biological system: DNA is transcribed into RNA, which is then translated into protein. This process emphasizes the role of DNA in storing genetic information and proteins as functional molecules.
What techniques are used in DNA fingerprinting, and what are its applications?
mediumAnswer: DNA fingerprinting involves extracting DNA, amplifying it using PCR, and then using gel electrophoresis to detect polymorphisms. It is used in forensic science for identifying individuals, in paternity tests, and in biodiversity studies to understand genetic variation.
Why is complementary base pairing essential in nucleic acid structures?
easyAnswer: Complementary base pairing is essential as it allows DNA to replicate accurately, ensures the proper transfer of genetic information during transcription, and maintains the structural integrity of both DNA and RNA.